Bottom feed floor mount transformer?

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wirebender

wirebender

Senior Member
Location
North Central Texas
I will be installing an Eaton 112.5KVA transformer on the floor, remotely fed from a lockable breaker so I won't be using a disconnect at the transformer.

Is there anything prohibiting me from bringing the feed into the bottom of the transformer, just like in a floor mounted switchgear?

PVC conduit, AL wire in a healthcare facility.
 
wirebender said:
I will be installing an Eaton 112.5KVA transformer on the floor, remotely fed from a lockable breaker so I won't be using a disconnect at the transformer.

Is there anything prohibiting me from bringing the feed into the bottom of the transformer, just like in a floor mounted switchgear?

PVC conduit, AL wire in a healthcare facility.
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Have you contacted Eaton for a drawing of the transformer?. Have you asked Eaton unless you are afraid to get an answer that you don't want to hear.
A drawing should include a plan view of the bottom that should illustrate areas that allow for cable entry.
BUT!!!! caution must be used as it is extremely important where the termination are located and orientated. Terminals must be oriented as sduch that the cables entering the bottom can be terminated on them. It is not all that uncommon that such cable entry be specified such that the transformer is manufactured for this application.
 
I've never had an issue bringing them in the bottom, but your best bet is to get Eaton's cutsheet to verify the proper location.
 
infinity said:
So these are specially designed transformers for bottom feed?
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I have never seen a dry transformer in that size range specifically designed for a bottom entry, and like Bob, have made bottom entries in these types of transformers many times.
 
At one of our local IAEI get-togethers there was mention of a NEMA change in regard to the ventilated bottom dry type transformer. I can't recall if it dealt with grounding or conduit entry. I am sending a e-mail to fellow forum member and NEMA rep. Bryan Holland, to see if he can elaborate on any changes.
 
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Given this new requirement in the 2014 NEC I would say that there is a concern for any alteration to the venting built into a transformer.

450.10 Grounding.
(A) Dry-Type Transformer Enclosures. Where separate
equipment grounding conductors and supply-side bonding
jumpers are installed, a terminal bar for all grounding and
bonding conductor connections shall be secured inside the
transformer enclosure. The terminal bar shall be bonded to
the enclosure in accordance with 250.12 and shall not be
installed on or over any vented portion of the enclosure.
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infinity said:
Given this new requirement in the 2014 NEC I would say that there is a concern for any alteration to the venting built into a transformer.
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That is most likely the "Change" I had in mind thinking it was NEMA as we are not on '14 here.
 
infinity said:
Given this new requirement in the 2014 NEC I would say that there is a concern for any alteration to the venting built into a transformer.
Click to expand...

I am not concerned, running the conductors in from the sides also alters and blocks the vents.

The instructions on the transformer say 'Enter below this line'. :)
 
The National Electrical Manufacturers Association (NEMA) published NEMA ST 20-2014 Dry Type Transformers for General Applications.

The reinstated and revised edition of NEMA ST 20 applies to single-phase and polyphase dry-type transformers (including autotransformers and non-current-limiting reactors) for supplying energy to power, heating, and lighting circuits, and designed to be installed and used in accordance with the National Electrical Code?. It also covers transformers with or without accessories having ratings of 1.2 kV class, 0.25 kVA through 4000 kVA.

NEMA ST 20 is one of the few standards in the marketplace that specifically addresses sound levels for this particular type of transformer. The U.S. Army Corps of Engineers still references it in their criteria documents. Changes in the latest version include a single average sound level table, more alignment with IEEE (Institute of Electrical and Electronics Engineers), and a new appendix providing a brief introduction to U.S. efficiency regulations.

NEMA ST 20-2014 may be downloaded at no cost or purchased in hardcopy for $71 on the NEMA website.

NEMA is the association of electrical equipment and medical imaging manufacturers, founded in 1926 and headquartered in Rosslyn, Virginia. Its 400-plus member companies manufacture a diverse set of products including power transmission and distribution equipment, lighting systems, factory automation and control systems, and medical diagnostic imaging systems. Total U.S. shipments for electroindustry products exceeds $100 billion annually.

http://www.nema.org/Standards/Pages/Dry-Type-Transformers-for-General-Applications.aspx
 
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